Axial flow compressor



June 11, 1963 G. D. FRASER AXIAL FLow COMPRESSOR Filed Jan. 31. 1961INVENTORS @HOVER D. FRA

BY\ Has A To NEY United States Patent Oii 3,093,300 Patented June 11,1963 ice New Jersey Filed Jan. 31, 1961, Ser. No. 86,164 2 Claims. (Cl.230-158) This invention relates to gas handling rotary machines havingat least two stages for gas compression or expansion and particularly tothat type of machine which is provided with male and female helicalintermeshing screw type rotors which, as they turn, positively displaceduid in a substantially axial direction with respect to the rotors ifthe machine be a compressor or pump, or, if a motor, the chamber formedby the rotors expands to produce the motive force.

The invention has to do more particularly with a machine of this typeoperating in stages, each stage having a pair of such rotor elements,and the second stage operating on the discharge of the rst stage.

It is an object of the invention to provide a construction in which theenclosing casing of lsuch a machine is compact and relatively simple tomanufacture.

A further object is to provide a casing for such a machine formed insections, one of which forms an intermediate passage between the stagesand eliminates the necessity of external conducting passagestherebetween. These objects are attained, in brief, by providing acasing containing first and second stages, each stage including a pairof intermeshing rotors cooperating with each other and the'. cas-ing toform a variable displacement chamber therebetween and mounted in axiallyspaced relationship to the rotors of the other stage, locating apartition between the first and second stages and engaging the end facesof the rotors of both stages to cooperate with the rotors to form thevariable displacement chambers of both stages, and providing thepartition with a passageway means for receiving gas discharged from thefirst stage and feeding `it to the second stage. In a specificembodiment of the invention, the partition is hollow and includes a pairof axially spaced walls, one wall containing a gas discharge outlet portfor the first stage and the other wall containing a gas inlet port forthe second stage with the two ports being angularly displaced from eachother relative to the axes of the rotors.

Other objects and advantages of the invention will be in part pointedout and -in part obvious hereinafter.

The drawing illustrates an improved form of the invention and includesFIGURE l, a longitudinal view of a two-stage compressor to which theinvention is applied, the casing being shown broken raway to disclosethe inner construction,

FIG. 2 is a sectional view in perspective taken along the line 2--2 ofFIG. 1 and showing the partition interposed between the two stages ofthe compressor,

FIG. 3 is a diagrammatic representation indicating the porting areasand, in part, the important flow areas of the uid handled by themachine, and

FIG. 4 is a cross section through the partition or intermediate sectionof the casing taken at the line 4-4 of FIG. l looking in the directionof the arrows.

Referring to the drawing and more particularly to FIG. l, the mach-inewhich is here illustrated as a two stage machine, is provided with afirst stage pair of rotors including a male rotor and a female rotor 12intermeshing and adapted to turn within the first stage section 14 ofthe casing. Rotors 10 and 12 tit within intersecting circular bores 16and 18, respectively, and their outer extremities form a substantialseal therewith and with each other, as is well known in the art, to forma variable displacement chamber which progresses from the inlet end ofthe casing to the discharge end. Each rotor 10 and 12 has a shaftextension 11 and 13 supported in parallel relationship in an inlet head22. When the machine is used as a compressor the chamber so formedpositively displaces fluid which has been introduced by way of the inlet20 in the inlet head 22 which provides an end face 24 abutting the endsof rotors 10 and 12 and which is provided with an inlet port 26 alsoindicated diagrammatically by the shaded portion so designated in FIG.3.

The secondfstage of the machine is housed within a second section 28 ofthe casing similarly provided with a pair of intersecting cylindricalbores 30 and 32 containing a shorter pair of rotors 34 and 36, theformer being the male rotor and the latter the female rotor, each havinga shaft extension 41, 43, respectively, supported in a discharge head38. Fluid being handled by rotors 3'4 and 36 is discharged into thedischarge head 38 having a discharge outlet 40and provided with a port42 also indicated in FIG. 3. The vshaded area connecting port 42 withdischarge 40 in FIG. 3 indicates the passage of discharge air or-otherworking uid in the discharge head 38.

Male rotors 10 and 34 are in this instance formed asl a unit with ashort cylindrical connecting section 44 therebetween, and likewisefemale rotors 12 and 36 are conneoted by a short cylindrical connectingsection 46. Casing sections A14 and 28 are provided with an intermediatecasing section or partition 48 which has two interconnected partscooperating with the rotors of the first and second stage to control thedischarge from the iirst stage rotors and to control the inlet to thesecond stage rotors. In this instance intermediate section `48 is hollowand provided with a plane faced wall S0 abutting the ends of rotors 10and 12 and the ends of the cylindrical bores l16 and 18. An outlet port52 is provided in the face of wall 50 to pass uid discharged from thefirst stage into the interior of section 48. A second wall 54 parallelto Wall 50 and abutting the inlet ends of second stage rotors 34 and 36is also provided with an inlet port 56 to convey fluid from the interiorof section 48 to the space between rotors 34 and 36. Intermediatesection 48 is formed in two symmetrical halves, being split as shown atthe joint 58, so as to iit about the portions 44 and 46. The portions ofsection `48 are held together in an encircling ange -60 formedintegrally with either the first or the second casing section 28 andarranged to abut the iiange 62 formed on the first casing section 14.Flanges 60 and 62 are suitably bolted together by the screws 64.

As above described, fluid entering the first casing section 14 isentrapped by rotors 10` and 12 and carried axially to the first stagedischarge ports 52 to be contained within the reservoir space within thehollow intermediate casing section 48. Such fluid is admitted to thesecond stage at port 56 to be engaged by rotors 34 and 36 and carriedaxially to discharge port 42 and thence discharged at outlet 40. As iswell understood in the art the space between lthe lobes and grooves ofthe rotors forms a distorted pyramid as indicated at the shaded portions66 and 68 in FIG. 3, becoming progressively smaller thereby compressingthe fluid contained therein. It is understood that the rotors 10 and 12and those shown at 34 and 36 are suitably driven from a shaft 70 adaptedto be attached to a suitable source of motive power (not shown) and therotors are suitably journaled in inlet head 22 and discharge head 38.The rotors may be coupled together by synchronizing gearing (not shown)or one may be driven by the other through the direct contacttherebetween.

Another feature of the porting arrangement as described hereinbefore, isthat there is no low spot for liquid to settle between stages and to bepicked up as a slug to enter the second stage. Any liquid in thecompressor,

such as used for coolingpurposes, flows tlu'ough the machinesubstantially without changing level or settling.

A bypass valve 78, positioned on the face of wall 54 of intermediatecasing section 48, controls the flow of fluid through a passage 80communicating outlet 40 directly with the interior of intermediatecasing section 48 and port 52. Such control is provided to penmit fluidto ow from port 52 into outlet 40 but to prevent return flow from outlet40 into the interior of intermediate casing section 48. Passage 80serves to bypass the operational flow path of the fluid in theintermediate casing section 48 and `in the second stage section 28 whenthe compressor is started, such bypass permitting fluid which isinitially compressed in the first stage section to ow out freelytherefrom through Vpassage 80 tinto outlet 40 until suficient pressureis built up in outlet 40 to cause valve 78 to close such that thereuponthe uid follows the operational path as hereinbefore described. Withsuch an arrangement, when starting the compressor, power for initialcompression of uid in the compressor is utilized to the best advantage.

To reinforce the end walls 50 and 54 suitable spacers 72 and 74 may beprovided surrounding the shaft portions 46 and 44, respectively, butpreferably they do not form bearings therewith which would necessitatedifficult machining of the intermediate casing 48.

As shown in FIG. 1 an interconnecting pipe 76 is provided to convey oilfrom the discharge head 38 to the inlet head 22 for circulation andlubrication of the bearings and gears. The lubrication system, not beinga feature of this invention, is not described in detail herein.

Thus, by the above construction are accomplished, among others, theobjects hereinbefore referred to.

I claim:

1. A plural stage axial flow gas handling machine comprising: a casingcontaining a pair of gas handling expansible-contractable positivedisplacement stages including first and second stages; each stageincluding a `pair of inter-meshing screw-type rotors cooperating witheach other to form an eXpansible-contractable positive displacementchamber therebetween and mounted in axially spaced relationship to therotors of the other stage; a partition secured to the casing and locatedbetween the rotors of said first and second stages; said partition beinghollow and including a pair of axially spaced walls, each of which islocated adjacent one of said stages and engages the end faces of therotors of that stage to cooperate with the rotors in forming theexpansible-contractable positive displacement chamber of that stage; oneof said walls containing an outlet port from the first stage and theother wall containing an inlet port for the second stage with said portsbeing angularly displaced from each other relative to a plane passingthrough the axes of the rotors; and said partition being formed in atleast two intertting arcuate sections which can be separated forassembly and disassembly of the machine.

2. The machine of claim 1 wherein: said casing is formed of at least twocasing sections, one casing section housing the first stage rotors andthe other housing the second stage rotors; and said partition isremovably secured to and between said two casing sections.

References Cited in the file of this patent UNITED STATES PATENTS1,164,546 Newland Dec. 14, 1915 1,443,764 Smith Jan. 30, 1923 1,531,607Green Mar. 31, 1925 1,561,364 Smith Nov. 10, 1925 1,626,768 Vollmann May3, 1927 2,009,137 Kleckner July 23, 1935 2,381,695 Sennett Aug. 7, 19452,804,260 Nilsson et al. Aug. 27, 1957 FOREIGN PATENTS 723,315 Germany vAug. 3, 1942 801,560 Germany Ian. 11, 1951

1. A PLURAL STAGE AXIAL FLOW GAS HANDLING MACHINE COMPRISING: A CASINGCONTAINING A PAIR OF GAS HANDLING EXPANSIBLE-CONTRACTABLE POSITIVEDISPLACEMENT STAGES INCLUDING FIRST AND SECOND STAGES; EACH STAGEINCLUDING A PAIR OF INTER-MESHING SCREW-TYPE ROTORS COOPERATING WITHEACH OTHER TO FORM AN EXPANSIBLE-CONTRACTABLE POSITIVE DISPLACEMENTCHAMBER THEREBETWEEN AND MOUNTED IN AXIALLY SPACED RELATIONSHIP TO THEROTORS OF THE OTHER STAGE; A PARTITION SECURED TO THE CASING AND LOCATEDBETWEEN THE ROTORS OF SAID FIRST AND SECOND STAGES; SAID PARTITION BEINGHOLLOW AND INCLUDING A PAIR OF AXIALLY SPACED WALLS, EACH OF WHICH ISLOCATED ADJACENT ONE OF SAID STAGES AND ENGAGES THE END FACES OF THEROTORS OF THAT STAGE TO CO-